(1) Field of the Invention
The invention relates to a protective tape separation method capable of joining an adhesive tape to a protective tape joined to the surface of a semiconductor wafer held by a ring-shaped frame via a supporting adhesive tape and separating the protective tape integrally with the adhesive tape from the semiconductor wafer with high precision, and to an apparatus using the same.
(2) Description of the Related Art
A semiconductor wafer (hereinafter, simply referred to as “wafer”) is thinned by processing the back side of the wafer by using a mechanical method such as grinding or polishing or a chemical method using etching. At the time of processing the wafer by using any of the methods, a protective tape is joined to the surface of the wafer to protect the surface on which a wiring pattern is formed. The back side of the wafer to which the protective tape is joined and which is polished is suction-held by a ring-shaped frame via a supporting adhesive tape. After that, the protective tape is separated from the surface of the wafer held on the ring-shaped frame for removal.
Concretely, the adhesive tape is joined to the surface of the protective tape by a roller and is separated to separate and remove the adhesive tape integrally with the protective tape from the surface of the wafer, and the adhesive tape and the protective tape are taken up. At the time of joining the adhesive tape to the surface of the protective tape, a non-adhesive thin plate is joined to a supporting adhesive tape on the joining start end side so as to prevent contact between the supporting adhesive tape on the joining start end side of the adhesive tape and the adhesive tape wrapped around a roller (refer to, for example, International Patent Publication WO97/08745).
The conventional protective tape separation method, however, has the following problems.
In recent years, with rapid progress in applications, reduction in thickness of a wafer is in demand and a wafer is thinned to 150 μm or less. In the case of holding a wafer W thinned in a state where a protective tape is joined to the wafer W by a supporting adhesive sheet DT from the back side of a ring-shaped frame f and separating the protective tape from the surface of the wafer, when a non-adhesive thin plate thicker than the wafer is joined to the supporting adhesive tape on the joining start end side of the adhesive tape, a gap G generates due to the difference between the thickness of the wafer and the thickness of a thin plate 61 as shown in FIG. 1. Consequently, pressure on the adhesive tape Ts with a roller 60 is uneven due to the gap G. The adhesive tape Ts is not firmly made close-contact with the end of a protective tape PT particularly at the joining start end due to the gap G. It causes a problem in that separation stability is low at the time of separating the adhesive tape Ts integrally with the protective tape PT.
The adhesive tape Ts can be joined to the surface of the protective tape PT uniformly from an end if the non-adhesive thin plate 61 is processed to be thinner than the wafer. There are, however, problems in that it is more difficult to adjust the thickness by coating the surface of a plate member with a non-adhesive material than thinning of the wafer W, and handling for joining the thin plate 61 to the supporting adhesive tape DT in a series of processes of a wafer is difficult.